Network security monitoring system employing bi-directional communication

ABSTRACT

The present invention provides for the receipt of a heartbeat message transmitted from a software agent within a host machine to a server-based agent manager. The server-based agent manager analyzes the heartbeat message to determine the identity of the sending software agent. The server-based agent manager then determines what information is to be included in a response message to the software agent. The server-based agent manager prepares the response message to be sent to the software agent. The server-based agent manager transmits the response message to the software agent over a bi-directional communication link between the software agent and the server-based agent manager. The software agent receives the response message; deserializes the response message; reviews the instructions within the response message; and performs operations necessary to carry out the instructions delivered in the response message.

FIELD OF THE INVENTION

The present invention relates to a computer-based system for capturingsecurity events from heterogeneous sources, normalizing such events to acommon schema and cross-correlating such normalized events with rules tocreate meta-events.

BACKGROUND

Computer networks and systems have become indispensable tools for modernbusiness. Today terabits of information on virtually every subjectimaginable are stored in and accessed across such networks by usersthroughout the world. Much of this information is, to some degree,confidential and its protection is required. Not surprisingly then,intrusion detection systems (IDS) have been developed to help uncoverattempts by unauthorized persons and/or devices to gain access tocomputer networks and the information stored therein.

Intrusion detection may be regarded as the art of detectinginappropriate, incorrect or anomalous activity within or concerning acomputer network or system. The most common approaches to intrusiondetection are statistical anomaly detection and pattern-matchingdetection. IDS that operate on a host to detect malicious activity onthat host are called host-based IDS (and may exist in the form of hostwrappers/personal firewalls or agent-based software), and those thatoperate on network data flows are called network-based IDS. Host-basedintrusion detection involves loading software on the system (the host)to be monitored and using log files and/or the host's auditing agents assources of data. In contrast, a network-based intrusion detection systemmonitors the traffic on its network segment and uses that traffic as adata source. Packets captured by the network interface cards areconsidered to be of interest if they match a signature.

Regardless of the data source, there are two complementary approaches todetecting intrusions: knowledge-based approaches and behavior-basedapproaches. Almost all IDS tools in use today are knowledge-based.Knowledge-based intrusion detection techniques involve comparing thecaptured data to information regarding known techniques to exploitvulnerabilities. When a match is detected, an alarm is triggered.Behavior-based intrusion detection techniques, on the other hand,attempt to spot intrusions by observing deviations from normal orexpected behaviors of the system or the users (models of which areextracted from reference information collected by various means). When asuspected deviation is observed, an alarm is generated.

Advantages of the knowledge-based approaches are that they have thepotential for very low false alarm rates, and the contextual analysisproposed by the intrusion detection system is detailed, making it easierfor a security officer using such an intrusion detection system to takepreventive or corrective action. Drawbacks include the difficulty ingathering the required information on the known attacks and keeping itup to date with new vulnerabilities and environments.

Advantages of behavior-based approaches are that they can detectattempts to exploit new and unforeseen vulnerabilities. They are alsoless dependent on system specifics. However, the high false alarm rateis generally cited as a significant drawback of these techniques andbecause behaviors can change over time, the incidence of such falsealarms can increase.

Regardless of whether a host-based or a network-based implementation isadopted and whether that implementation is knowledge-based orbehavior-based, an intrusion detection system is only as useful as itsability to discriminate between normal system usage and true intrusions(accompanied by appropriate alerts). If intrusions can be detected andthe appropriate personnel notified in a prompt fashion, measures can betaken to avoid compromises to the protected system. Otherwise suchsafeguarding cannot be provided. Accordingly, what is needed is a systemthat can provide accurate and timely intrusion detection and alertgeneration so as to effectively combat attempts to compromise a computernetwork or system.

SUMMARY OF THE INVENTION

In one embodiment, the invention is a method for providingbi-directional communication between software agents and a server-basedsoftware agent manager. The method includes receiving, at a server-basedagent manager, a heartbeat message from a software agent. The methodalso includes identifying the software agent at the agent manager. Themethod also includes determining how to respond to the heartbeat messageform the software agent. The method further includes preparing aresponse message to be sent from the agent manager to the softwareagent. Moreover, the method includes sending the response message fromthe agent manager to the software agent.

In an alternate embodiment, the invention is a system. The systemincludes a bi-directional communication link between a software agentincluded within a host machine and a server-based agent manager. Thesystem further includes an interface component to transmit messages ontoand receive messages from the bi-directional communication link.Moreover, the system includes a heartbeat receiver component todeserialize messages received by the interface component from theserver-based agent manager.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIG. 1 illustrates one embodiment of a computer-based system forcapturing, normalizing and reporting security events from heterogeneoussources configured in accordance with the present invention;

FIG. 2 illustrates procedures followed by an agent configured inaccordance with an embodiment of the present invention when collecting,normalizing and reporting security event data;

FIG. 3 illustrates procedures followed by a manager configured inaccordance with an embodiment of the present invention when analyzingsecurity event data and generating alerts based thereon;

FIG. 4 illustrates the integration of multiple agents within a hostmachine in accordance with an embodiment of the present invention.

FIG. 5 illustrates the intergration of an agent within a device (e.g.,router) in accordance with an embodiment of the present invention .

FIG. 6 illustrates operation of an agent normalize component inaccordance with an embodiment of the present invention.

FIG. 7 illustrates an agent normalize component in accordance with anembodiment of the present invention.

FIG. 8 illustrates an agent aggregate component in accordance with anembodiment of the present invention.

FIG. 9 is a flow chart illustrating a method, according to oneembodiment of the invention, of configuring a software agent.

FIG. 10 is a flow chart illustrating a method, according to oneembodiment of the invention, of automatically altering the operation ofa software agent.

FIG. 11 is a diagrammatic representation of bi-directional communicationbetween a software agent within a host and an agent manager.

FIG. 12 is a flow chart illustrating a method, according to oneembodiment of the invention, showing bi-directional communicationbetween a software agent and an agent manager.

DETAILED DESCRIPTION

Described herein is a computer-based system for capturing securityevents from heterogeneous sources, normalizing such events to a commonschema and cross-correlating such normalized events with rules to createmeta-events. The system (one embodiment of which is manifest as computersoftware), enables aggregation, correlation, detection, andinvestigative tracking of suspicious network activities from multiplesecurity devices. The present system also supports response management,ad-hoc query resolution, reporting and replay for forensics analysis,and graphical visualization of network threats and activity.

Although the present system will be discussed with reference to variousillustrated examples, these examples should not be read to limit thebroader spirit and scope of the present invention. For example, theexamples presented herein describe distributed agents, managers andconsoles, which are but one embodiment of the present invention. Thegeneral concepts and reach of the present invention are much broader andmay extend to any computer-based or network-based security system. Also,examples of the messages that may be passed to and from the componentsof the system and the data schemas that may be used by components of thesystem are given in an attempt to further describe the presentinvention, but are not meant to be all-inclusive examples and should notbe regarded as such.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on datawithin a computer memory. These algorithmic descriptions andrepresentations are the means used by those skilled in the computerscience arts to most effectively convey the substance of their work toothers skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of steps leading to a desiredresult. The steps are those requiring physical manipulations of physicalquantities. Usually, though not necessarily, these quantities take theform of electrical or magnetic signals capable of being stored,transferred, combined, compared and otherwise manipulated. It has provenconvenient at times, principally for reasons of common usage, to referto these signals as bits, values, elements, symbols, characters, terms,numbers or the like. It should be borne in mind, however, that all ofthese and similar terms are to be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities. Unless specifically stated otherwise, it will be appreciatedthat throughout the description of the present invention, use of termssuch as “processing”, “computing”, “calculating”, “determining”,“displaying” or the like, refer to the action and processes of acomputer system, or similar electronic computing device, thatmanipulates and transforms data represented as physical (electronic)quantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

As indicated above, one embodiment of the present invention isinstantiated in computer software, that is, computer readableinstructions, which, when executed by one or more computerprocessors/systems, instruct the processors/systems to perform thedesignated actions. Such computer software may be resident in one ormore computer readable media, such as hard drives, CD-ROMs, DVD-ROMs,read-only memory, read-write memory and so on. Such software may bedistributed on one or more of these media, or may be made available fordownload across one or more computer networks (e.g., the Internet).Regardless of the format, the computer programming, rendering andprocessing techniques discussed herein are simply examples of the typesof programming, rendering and processing techniques that may be used toimplement aspects of the present invention. These examples should in noway limit the present invention, which is best understood with referenceto the claims that follow this description.

Referring now to FIG. 1, an example of a computer-based system 10architected in accordance with an embodiment of the present invention isillustrated. System 10 includes agents 12, one or more managers 14 andone or more consoles 16 (which may include browser-based versionsthereof). In some embodiments, agents, managers and/or consoles may becombined in a single platform or distributed in two, three or moreplatforms (such as in the illustrated example). The use of thismulti-tier architecture supports scalability as a computer network orsystem grows.

Agents 12 are software programs that provide efficient, real-time (ornear real-time) local event data capture and filtering from a variety ofnetwork security devices and/or applications. The primary sources ofsecurity events are common network elements including firewalls,intrusion detection systems and operating system logs. Agents 12 cancollect events from any source that produces event logs or messages andcan operate at the native device, at consolidation points within thenetwork, and/or through simple network management protocol (SNMP) traps.

Managers 14 are server-based components that further consolidate, filterand cross-correlate events received from the agents, employing a rulesengine 18 and a centralized event database 20. One role of manager 14 isto capture and store all of the real-time and historic event data toconstruct (via database manager 22) a complete, enterprise-wide pictureof security activity. The manager 14 also provides centralizedadministration, notification (through one or more notifiers 24), andreporting, as well as a knowledge base 28 and case management workflow.The manager 14 may be deployed on any computer hardware platform and oneembodiment utilizes an Oracle™ database. Communications between manager14 and agents 12 may be bi-directional (e.g., to allow manager 14 totransmit commands to the platforms hosting agents 12) and encrypted. Insome installations, managers 14 may act as concentrators for multipleagents 12 and can forward information to other managers (e.g., deployedat a corporate headquarters).

Consoles 16 are computer- (e.g., workstation-) based applications thatallow security professionals to perform day-to-day administrative andoperation tasks such as event monitoring, rules authoring, incidentinvestigation and reporting. Access control lists allow multiplesecurity professionals to use the same system and event database, witheach having their own views, correlation rules, alerts, reports andknowledge base appropriate to their responsibilities. A single manager14 can support multiple consoles 16.

In some embodiments, a browser-based version of the console 16 may beused to provide access to security events, knowledge base articles,reports, notifications and cases. That is, the manager 14 may include aweb server component accessible via a web browser hosted on a personalcomputer (which takes the place of console 16) to provide some or all ofthe functionality of a console 16. Browser access is particularly usefulfor security professionals that are away from the consoles 16 and forpart-time users. Communication between consoles 16 and manager 14 isbi-directional and may be encrypted.

Through the above-described architecture the present invention cansupport a centralized or decentralized environment. This is usefulbecause an organization may want to implement a single instance ofsystem 10 and use an access control list to partition users.Alternatively, the organization may choose to deploy separate systems 10for each of a number of groups and consolidate the results at a “master”level. Such a deployment can also achieve a “follow-the-sun” arrangementwhere geographically dispersed peer groups collaborate with each otherby passing primary oversight responsibility to the group currentlyworking standard business hours. Systems 10 can also be deployed in acorporate hierarchy where business divisions work separately and supporta rollup to a centralized management function.

Examining each of the various components in further detail, we beginwith the agents 12. Agents 12 are used to collect, reduce and normalizethe enormous amount of data that is generated by a network's securitydevices before a manager 14 acts on the data. As will become evident,this process goes beyond simple log consolidation. Before presentingthose details, however, and to understand why such measures aredesirable, some background regarding how analysts currently cope withsecurity event information generated by multiple network devices isuseful.

Conventional intrusion detection systems can help an analyst detect anattack directed at a network resource such as a server. Usually, suchinvestigations are launched in response to an alert generated by theIDS. As a first step after receiving such an alert, an analyst mightreview perimeter router logs to see if a router associated with thenetwork passed a packet that triggered the alert. If such a packet werediscovered, the analyst would likely then want to review one or morefirewall logs to see if any existing filters blocked the suspect packet.Assume, for the sake of this example, the suspect packet got past anyfirewalls; further investigation would be necessary to determine whetherthe integrity of the server itself was compromised. Such an integritycheck may be performed using a conventional software application such asTripwire, which is a file integrity checker employing MD5 checksums, tosee which files, if any, had been accessed or modified. Finally, theanalyst may have to examine a Syslog or an EventLog from the subjectserver, as well as any tcpdump data collected by a dedicated tcpdumphost, for the segment of time surrounding the attack to determine whatactually happened.

By this time the analyst has accessed many different systems and lookedat several different types of logs in an effort to distill acomprehensive view of the attack. This can be a significant amount ofwork, and time taken in such review and analysis is time lost from thevitally important tasks of securing the network and restoring thecompromised server to make sure that no other systems will be affected.The present invention helps to minimize the time spent on such analysisby consolidating all the relevant information in a single loggingfacility, allowing the analyst to look at the data in whatever sequenceor depth he or she requires.

More than just consolidation, though, the present agents 12 provide datanormalization, which is of great benefit when an analyst must deal withsecurity incidents in a heterogeneous network environment. To understandwhy normalization is helpful consider a typical enterprise environment,which consists of many different types of network devices ranging fromborder routers and VPN devices, to firewalls and authentication servers,and a wide range of application servers such as web servers, e-mailservers and database servers. Each of these devices generates logs that,as described above, are sources of data to a security analyst. However,it is seldom, if ever, the case that two manufactures will use the sameevent logging mechanism or format their event logs identically. Forexample a Cisco Systems PIX™ firewall will not report an accepted packetin the same way as a Check Point firewall or even in the same fashion asa Cisco Systems router.

An example of the types of various reports that might be generated bydifferent network devices is presented below in Table 1, which showsexamples of logs from different network devices, each reporting the samepacket travelling across a network. In particular, these logs representa remote printer buffer overflow that connects to IIS servers over port80.

TABLE 1 Examples of Event Logs for Different Network Devices. NetworkEvent Log Device Check Point “14” “21Dec2001” “12:10:29” “eth-s1p4c0”firewall “ip.of.firewall” “log” “accept” “www-http” “65.65.65.65”“10.10.10.10” “tcp” “4” “1355” ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″“firewall” “ len 68” Cisco Systems Dec 21 12:10:27: %SEC-6-IPACCESSLOGP:list 102 router permitted tcp 65.65.65.65(1355) -> 10.10.10.10(80), 1packet Cisco Systems Dec 21 2001 12:10:28: %PIX-6-302001: Built inboundPIX firewall TCP connection 125891 for faddr 65.65.65.65/1355 gaddr10.10.10.10/80 laddr 10.0.111.22/80 Snort [**][1:971:1] WEB-IIS ISAPI.printer access [**] [Classification: Attempted Information Leak][Priority: 3] 12/21-12:10:29.100000 65.65.65.65:1355 -> 10.10.10.10:80TCP TTL:63 TOS:0x0 ID:5752 IpLen:20 DgmLen:1234 DF***AP*** Seq:0xB13810DC Ack: 0xC5D2E066 Win: 0x7D78 TcpLen: 32 TCP Options (3) => NOPNOP TS: 493412860 0 [Xref => http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0241] [Xref =>http://www.whitehats.com/info/IDS533]

The Check Point record contains the following fields: event id, date,time, firewall interface, IP address of the firewall interface, loggingfacility, action, service, source IP, target IP, protocol, source port,some Check Point specific fields and then the size of the datagram. Thisreport is, to say the least, difficult for a human analyst to read(especially with all the empty fields that are represented by doublequotes). The Cisco router has a different format: date, time, loggingfacility, event name, source IP, source port, target address, targetport, and number of packets. The Cisco PIX firewall, which is producedby the same manufacturer as the router, uses yet another format: date,time, event name, source IP, source port, translated address or targetaddress, target port, local address, and local port.

The final record is a Snort alert that claims this traffic wasmalicious. Snort is a well-known IDS and the fields it populates are:exploit or event name, classification, priority, date, time, source IP,source port, target IP, target port, protocol, TTL (time to live), typeof service, ID, IP length, datagram length, tcp flags, sequence number,acknowledgement number, window size, and tcp length. Snort also reportsadditional data such as references to investigate the exploit.

Agents 12 may be deployed in connection with some or all of these (andother) network components and applications. For example, in FIG. 1,agent 12 a is deployed in connection with an IDS (such as Snort). Agent12 b is deployed in connection with a firewall (such as the Check Pointfirewall and/or the Cisco PIX firewall). Agent 12 c is deployed inconnection with other network components or agents (e.g., a router).Each of these agents receives the event information from its associatednetwork device or application in that device's or application's nativeformat and converts (or normalizes) the information to a common schema.This normalization allows for later storage of the event information ina format that can more readily be utilized by an analyst.

Many normalized schemas can be used and, in general, choosing the fieldsof a common schema may be based on content rather than semanticdifferences between device logs and/or manufacturers. To accomplish thisnormalization, agents 12 are equipped with a parser configured toextract values from the events as reported by the individual networkdevices/applications and populate the corresponding fields in thenormalized schema. Table 2 is an example of a normalized schema for thedata reported by the devices in Table 1.

TABLE 2 Common Schema Representation of Event Data Event DeviceAdditional Date Time Name Src_IP Src_Port Tgt_IP Trg_Port Type data 21Dec. 01 12:10:29 accept 65.65.65.65 1355 10.10.10.10 80 Check Point 21Dec. 01 12:10:27 list 102 65.65.65.65 1355 10.10.10.10 80 Cisco Routerpermitted tcp 21 Dec. 01 12:10:28 built inbound 65.65.65.65 135510.10.10.10 80 Cisco tcp connection PIX 21 Dec. 01 12:10:29 WEB-IIS65.65.65.65 1355 10.10.10.10 80 Snort TCP TTL:63 ISAPI.printer TOS: 0x0ID:5752 access IpLen:20 DgmLen: 1234 DF *** AP*** Seq: 0xB13810DC Ack:0xC5D2E066 Win: 0x7D78 TcpLen: 32 TCP Options (3) => NOP NOP TS:493412860 0

Table 2 reports the same four events described earlier, this time in anormalized fashion. Each of the agents 12 is configured to extract therelevant data from events reported by its associated networkdevice/application and map that data to the corresponding common schemarepresentation. For instance the Check Point firewall reports a targetport as www-http, not as port 80 as is the case for most other networkdevices. Therefore an agent 12 associated with the Check Point firewallis configured with an appropriate lookup mechanism (e.g., a table) toensure that “www-http” as reported by the firewall gets translated into“port 80” when the agent 12 reports the event to the manager 14.

Similarly, the agents 12 may need to be configured to convert thedate/time stamp formats used by the various network devices/applicationsinto a common date/time representation. That is, because the differentnetwork devices/applications all use different date/time formats, theagents cannot simply report the date/time stamps reported by thedevice/application. Instead, the agents 12 may be configured to convertlocal date/time stamps to a universal date/time notation, such asGreenwich Mean Time.

In addition to normalizing event data by fields, agents 12 can parse theevent data stream and set field values based on conventions andpractices of the organization. For example, the variety of eventseverity levels that devices produce can all be normalized at the agentlevel into a single, consistent hierarchy.

Thus, agents 12 collect and process events generated by heterogeneousnetwork devices/applications throughout an enterprise. Alerts can comefrom routers, e-mail logs, anti-virus products, firewalls, intrusiondetection systems, access control servers, VPN systems, NT Event Logs,Syslogs, and other sources where security threat information is detectedand reported. In some embodiments, each event generator has an agent 12assigned to collect all relevant security information, while in otherembodiments agents are shared among two or more event generators. Thus,depending on the device/application to be monitored and the in-placeinfrastructure, a choice is provided for simple log parsing and loading,network listening (e.g., through SNMP traps), installation onaggregation points (Syslog servers and concentrators) and fulldistribution to all security-relevant devices.

In addition to collecting and normalizing data from security devices,the agents 12 intelligently manage the data with:

-   -   Filtering: each agent 12 can be configured according to        conditions by which data will be collected and sent to the        manager 14. This helps to reduce the need to collect and manage        large volumes of unwanted data.    -   Aggregation: Based on the time period selected, the agents 12        can collect duplicate alerts but send only a single message with        a count of the total number of such alerts to the manager 14.        This helps reduce the amount of traffic transmitted across the        network.    -   Batching: Agents 12 can be configured to send a collection of        alerts at one time rather than sending alerts immediately after        each occurrence.

FIG. 2 illustrates the various processes performed by agents 12 from thepoint of view of the event information. Initially, at step 30, the rawevent information is received or collected from the native networkdevice or application in that device's/application's native format. Atthis point (or, optionally, following normalization), data filters maybe applied to reduce the volume of data being passed for furtheranalysis (step 32). Such filtering is optional and may involve assessingthe captured data against one or more conditions to determine whether ornot the data is relevant for further analysis.

Thereafter, the event data is normalized at step 34. As indicated above,the normalization may occur at the field and/or the field value level.Further, the normalization may involve translation of the field valuesinto nomenclatures/formats used across an enterprise.

Following normalization, the event data may, optionally, be aggregated(step 36) before being transmitted to the manager 14 (step 38). Thetransmissions may occur as the events are captured or may be made on abatched basis. In either case, the messages used to transmit the eventdata preferably include all of the source fields of an event. Bydelivering the entire event data set (i.e., all of the source fields)organized in a consistent format (i.e., the common schema), powerfulupstream data management, cross-correlation, display and reporting isavailable to the security team. In some embodiments the event data isdiscarded after successful transmission to the manager 14, but in othercases the data may be cached for a time at the agent 12 to permit laterreplay of the data.

Referring again to FIG. 1, the manager 14 includes one or more agentmanagers 26, which are responsible for receiving the event data messagestransmitted by the agents 12. Where bi-directional communication withthe agents 12 is implemented, these agent managers 26 may be used totransmit messages to the agents 12. If encryption is employed foragent-manager communications (which is optional), the agent manager 26is responsible for decrypting the messages received from agents 12 andencrypting any messages transmitted to the agents 12.

Once the event data messages have been received (and if necessarydecrypted), the event data is passed to the rules engine 18. Rulesengine 18 is at the heart of the manager 14 and is used tocross-correlate the event data with security rules in order to generatemeta-events. Meta-events, in the context of the present invention, areinstances of (usually) multiple individual event data elements (gatheredfrom heterogeneous sources) that collectively satisfy one or more ruleconditions such that an action is triggered. Stated differently, themeta-events represent information gathered from different sensors andpresented as correlated results (i.e., the decision output of the rulesengine 18 indicating that different events from different sources areassociated with a common incident as defined by one or more rules).

The actions triggered by the rules may include notifications transmitted(e.g., via notifier 24) to designated destinations (e.g., securityanalysts may be notified via the consoles 16, e-mail messages, a call toa telephone, cellular telephone, voicemail box and/or pager number oraddress, or by way of a message to another communication device and/oraddress such as a facsimile machine, etc.) and/or instructions tonetwork devices (e.g., via agents 12 or via external scripts or programsto which the notifier 24 may pass arguments) to take action to thwart asuspected attack (e.g., by reconfiguring one or more of the networkdevices, and or modifying or updating access lists, etc.). Theinformation sent with the notification can be configured to include themost relevant data based on the event that occurred and the requirementsof the analyst. In some embodiments, unacknowledged notifications willresult in automatic retransmission of the notification to anotherdesignated operator.

As discussed below, when meta-events are generated by the rules engine18, on-screen notifications may be provided to consoles 16 to promptusers to open cases for investigation of the events which led to thenotification. This may include accessing knowledge base 28 to gatherinformation regarding similar attack profiles and/or to take action inaccordance with specified procedures. The knowledge base 28 containsreference documents (e.g., in the form of web pages and/or downloadabledocuments) that provide a description of the threat, recommendedsolutions, reference information, company procedures and/or links toadditional resources. Indeed, any information can be provided throughthe knowledge base 28. By way of example, these pages/documents can haveas their source: user-authored articles, third-party articles, and/orsecurity vendors' reference material.

The rules engine 18 is based on a RETE engine configured to preserveevent information state over configurable time windows so as to providecorrelation of the event data according to specified rules. Correlationis generally regarded as a process of bringing information items intomutual relation. In the context of the present invention, correlationthrough rules engine 18 provides the ability to access, analyze, andrelate different attributes of events from multiple sources to bringsomething to the attention of an analyst that might (or likely would)have otherwise gone unnoticed. In other words, the rules engine 18provides the ability to determine what type of incident is representedby a collection of events reported by a number of heterogeneous networkdevices and/or applications. Because the collected event data isnormalized into a common event schema, correlation can be performedutilizing any field including, but not limited to, geography, devicetype, source, target, time thresholds, and/or event type. Based onalerts generated by the rules engine 18, operators are provided with aworkflow for investigating these incidents.

Turning to FIG. 3, the manager 14 receives (step 40) and analyzes (step42) the event data reported by agents 12 in real-time (or near real-timeowing to network latencies and depending upon whether or not batchedmessage transmission is used) according to a set of flexible rules. Therules define which events generate an alert, when those events generatean alert, and what actions are associated with the alert. Hence, therules may be written to contain event conditions, thresholds, andactions. In some embodiments the rule conditions may be specified usingBoolean operators and/or database queries. When incoming events match aparticular rule's conditions and thresholds, causing a meta-event to begenerated (step 44), the rule automatically fires the action that hasbeen defined (step 46). Such actions can include, but are not limitedto: executing a pre-determined command or script, logging the alert,sending the alert to the consoles 16, sending the alert to notificationdesignees, setting custom severity levels for the alert based oncumulative activity, adding a source to a suspicious list or a target toa vulnerable list, and/or a combination of these actions.

Rules may be created at the manager 14 and/or at the consoles 16 using aflexible scripting language. An example of a rule might be:

-   -   If (an ids evasion attack) occurs from the same source ip        address) (3 times) within (2 minutes) then (send message to        console) and (notify the security supervisor via pager).

In this example, the incoming event data would be compared against therule conditions and thresholds (in the above example 3 events thatsatisfy the condition of an IDS evasion attack are required and all mustoriginate from a common source IP address and be detected within 2minutes of each other), and if those criteria are satisfied thedesignated actions (here, sending an alert message to the consoles 16and also notifying a security supervisor via a pager) would beperformed. The correlation rules that operate on the events evaluatethreats and attacks according to selected criteria (e.g., degree ofthreat, level of success, vulnerability of target and value of target)and generate alerts according to a security intelligence taxonomy thatfocuses attention on the most dangerous and potentially most damagingattacks. For example, threats to network assets that are deemed not tohave succeeded or that are not likely to succeed may be coded green,while those that have succeeded or have a high probability of successmight be coded red. The value of the security information taxonomy liesin its ability to eliminate false positives while clearly identifyingreal threats to vulnerable and valuable assets.

In general, the rules may be designed to capture threats and attacksthat are typical in large, diverse networks and may be organized toprovide multiple lines of defense by detecting specific activities andgrouping them according to level of threat:

-   -   Reconnaissance zone transfer, port scan, protocol, scanning,        etc.    -   Suspicious illegal outgoing traffic, unusual levels of alerts        from the same host, etc.    -   Attack overflow, IDS evasion, virus, denial of service, etc.    -   Successful compromise of a backdoor, root compromise, covert        channel exploit, etc.

Similar events and signatures may be grouped into rule categories thatcan be utilized by the rules to insulate the rule from changes invendor-specific event details. For example, event names may changebetween product releases or new devices may be added to the networkinfrastructure with a new set of nomenclature. Since the rule categoriesmap similar signatures into a single name that is used by the rulesengine, if an individual network device changes taxonomy, only themapping is changed, not the rule definition. Therefore, despite changesin individual devices, the investment in custom defined rules ispreserved.

After the events are processed by rules engine 18, the raw event data aswell as any meta-events that were generated are stored in database 20(step 48). In some embodiments, the raw event data may be stored priorto or concurrently with processing of the data by rules engine 18.Regardless of the sequence, such storage of the event data (and the metaevents generated by the rules engine 18) preserves a historical recordof the event traffic and allows for replaying of the events through anexisting or a new rule set (either at the manager 14 or the consoles 16)in order to assess the efficacy of new rules, for training purposes,and/or for case investigation.

Correlation via the rules ensures that credible threats and attacks cometo the attention of the security staff on a high-priority basis. Henceonce an alert is received, the operator can perform in-depth analysisand take aggressive action secure in the knowledge that the effort iswell spent. When a rule match is reported to a console 16, the analystcan quickly drill down (through an associated graphical user interface)to see all of the individual events that caused the rule to fire. Ifnecessary, the analyst can investigate even further to see all of theindividual data elements captured for those events.

When action is required, the present invention provides a full set oftools and services for the operator. Resources such as the ruledefinition, a knowledge base article containing company policies andrecommended actions, and the development of a complete case docketdescribing the problem assist the operator in responding immediately tocritical security threats. If necessary, the operator can proactivelydeal with an attack by launching specific applications or scripts fromthe console 16 to reconfigure device settings or change accessprivileges.

The console 16 provides a centralized view into the security status ofan enterprise and gives administrators, analysts, and operators aninterface to perform security management tasks. In various embodiments,the console provides event display in real-time or in replay mode (i.e.,the ability to playback events from a given time period according to aVCR or DVD metaphor). Replay may be had from the events stored indatabase 20 or, in some instances, from caches associated with agents12. This latter form of replay is especially useful because it providesimproved simulation of actual network conditions as the events areplayed out across the same network as during the original attack.

Consoles 16 also provide operators with complete drill-down capabilityfrom the highest level of detail (e.g., the entire rage of events) tothe lowest level of detail (e.g., fields within a single event). Thisallows analysts to probe at whatever level of detail is required to gainfurther insight into an attack and assess vulnerability. This varyinglevel of detailed analysis is made possible because the agents 12 reportall of the event data fields, not merely a subset thereof. By way ofexample, one tool provides analysts with the ability to quickly seesimilar characteristics of events using a cursor control operation, suchas a mouse click. For example, if analysts are presented with ameta-event alert that consists of, say, twenty or more individual eventsreported by several different agents associated with different networkdevices, the present user interface associated with consoles 16 allowsthe analyst to quickly visualize only the common fields of these events(e.g., such as a source IP address) by simply highlighting the eventsand performing a mouse click/select operation.

Once security personnel have been notified of a meta-event, they canutilize the knowledge base to determine the appropriate actions. Inaddition, security analysts may undertake investigations of eventsand/or meta-events. In general, such matters can be assigned toso-called cases. Stated differently, cases create a workflow andoversight environment for situations where there are suspicious eventsrequiring further investigation. Once a case is created, it can beassigned to an operator, investigated, and resolved based on thebusiness policies and practices of the enterprise (e.g., as documentedin knowledge base 28). The security staff can also add narration andevent information to a case, or view open cases to determine theirstatus and any required next steps.

Consoles 16 also provide a front-end for the administration of theentire system 10. This may include system configuration such as settingup operators, notification, agent behavior, etc. User management (suchas creating and modifying users, access, roles, and responsibilities),rules management (e.g., authoring, viewing, and updating rules), andworkflow management (e.g., setting up the flow of actions taken when anevent is received) may also be handled through the consoles 16. Finally,the consoles 16 allow for remote access, thus supporting divisionalresponsibility and “follow-the-sun” management.

The agents 12 described above are configurable by either manual processor via automatic processing. FIG. 4 illustrates the integration ofmultiple agents 12 within a host machine. FIG. 5 illustrates theintegration of an agent 12 within a device (e.g., router). In theexemplary embodiment, the agent 12 may include a combination ofcomponents. The components are software modules developed usingtechniques and programming languages well known in the art. In oneembodiment, the agent 12 includes an agent normalize component 54, atime correction component 56, an agent aggregate component 58, an agentbatch component 60, an agent resolver component 62, an agent transportcomponent 64, and multiple additional components 66. Use of any or allof these components is optional in any given implementation. Referringto FIG. 4, the agent resolver component 62 and agent transport component64 may be shared by multiple agents within a host machine.

Associated with each agent 12 is a corresponding configuration file. Inthe exemplary embodiment the configuration file is a text file in whicheach line is an instruction to include a component (e.g., agentaggregate component 58) within an agent 12. It is through updating theinstructions within the configuration file that agent 12 achievesmodularity. In the exemplary embodiment an instruction may be added,deleted, or modified.

Moreover, the agent 12 is not limited to the components described above.In promoting the scalability and flexibility of the agent 12, additionalcomponents 66 may be created and included within the agent in futurereleases or according to customer requests/needs. As explained above theagent 12 may be configured manually. Thus, depending on the customersneeds the agent 12 may be configured through manual entries by a user(e.g., via console/browser interface 16) or through an automatedprocess. Such manual configuration may include merely modifying aconfiguration. In one embodiment, the configuration file is an asciitext file. Automated updates may include running a script file or anyother technique well known in the art to update one or multiple agents.Moreover, the agent manager 26 may automatically update agents 12 basedon analysis supported by the rules engine 18 and knowledge base 28.

The following is a description of each component named above:

Agent Normalize Component

In one embodiment of the present invention, security events are firstprocessed by the agent normalize component 54. The operation of theagent normalize component 54 is described with reference to FIG. 6. Atblock 68, the agent normalize component 54 receives the security eventfrom the security device being monitored. This can involve the securitydevice directly reporting the security event to the agent normalizecomponent 54, the agent normalize component 54 accessing some sharedmemory space, or the agent normalize component 54 gaining access to thesecurity event in any other channelized fashion.

The security event, as received, is an event data stream characterizedby several values that need to be parsed and extracted. The data streamand the values contained therein are in the format of the network devicethat generated the event. Some example data streams are given above foran example event as reported by a Check Point firewall, a Cisco Systemsrouter, a Cisco Systems PIX firewall, and the Snort IDS.

In block 70, the normalize component 54 parses the received event recordfor these values. The parser is configured to be able to determine thetype of event from the data field and to extract and interpret thevalues based on this determination. That is, the parser is configured tointerpret the syntax, semantics, type and format of the reported eventto extract the values.

In one embodiment, the parser is implemented using a descriptor filethat is declaratively configurable. That is, the descriptor filecontains declarative statements, such as Regular Expressions, that areinterpreted as a high-level language. The descriptor file contains allpossible formats for security events reported by the monitored networkdevice. Thus, the received event data stream can be matched to thepossible event types, and the key values can be extracted andinterpreted to create a parsed event that is organized by values. Such aparser is configurable without programming language coding, thusimproving the flexibility of the agents.

The extracted values are then used to populate the fields of thenormalized schema. The schema population is done at block 72, where theAgent normalize component 54 maps the extracted values to various fieldsof the normalized schema to create a normalized event that the systemcan use to correlate with other normalized events from heterogeneousnetwork devices. In one embodiment, the mapping is content based, ratherthan semantic based, to increase the efficiency of the normalized schemaand to aid in correlating the heterogeneous events. For example, in thedemonstration of Table 2 above, no matter where or in what format thevalue for the target port appeared in the event log, the value wasalways mapped to the Tgt_Port field of the normalized schema because allthe values had the same content.

Embodiments of the agent normalize component 54 are further describedwith reference to FIG. 7. A security event in the form of an event datastream 75 is parsed by the parser 83 to create a parsed security event76 that can be mapped to a normalized schema 78. The event data stream75 is raw event data.

The parser is configured to identify the kind of event represented bythe raw event data and interpret the values contained in the eventstream. For example an event data stream such as “User logged in from10.10.10.10” can be parsed into “source: User,” “action: logged in,”“source IP: 10.10.10.10.” The event can be identified as a log in typeevent by matching an expression such as “* logged in from *.” In oneembodiment the parser 83 is implemented declaratively using RegularExpression.

The values of the parsed security event 76 are then used to populate thefields of a normalized event conforming to the normalized event schema78. Map 82 performs this mapping. For example, map 82 populates Field 2of the normalized schema 78 with Value 1 of the parsed security event76. In other words, map 82 maps Value 1 to Field 2.

Map 82 can perform simple mapping, such as the mapping of Value 1 toField 2. For example, with reference to Table 2 above, the target IPvalue reported by the Check Point firewall was used to populate theTgt_IP field of the normalized schema. Furthermore, map 82 can use atranslator 80 to compensate for any semantic differences between thevalues as reported by the network device and the semantics used by thenormalized schema. For example, the Check Point firewall value or“www-http” was translated to “80” when mapped to the Trg_Port field inTable 2. The translator 80 can be implemented using a lookup table orany other means for mapping.

The translator 80 can also perform other functions, such as valuescaling. For example, if Value 2 represented the seriousness of thesecurity event as determined by the network device, this seriousness maybe on a different scale than the one used by the normalized schema 78.In one embodiment, the normalized schema 78 uses four severity levels:low, medium, high, and very high.

Thus, if the scale used by the network device has eight levels, onepossible severity mapping would map severity level 1-2 to low, 3-4 tomedium, and so on. However, other mappings may be more appropriatedepending on the network device. For example, if a network deviceoverrates the seriousness of events as compared to other heterogeneousnetwork devices, its reported severity may be mapped to lower severitylevels to normalize the severities in relation to these other networkdevices.

Furthermore, map 82 can also map one value to any number of fields. Thisis demonstrated in FIG. 7 by Value 3 being used to populate both Field 1and Field 5. For example, the seriousness of the security event can bemapped through a translator 80 that performs the severity mapping, andcan also mapped unaltered, that is as originally reported by the networkdevice, to another field to preserve all the values contained in thesecurity event.

Similarly, any number of values can be mapped to a single field wheremultiple values are needed to fully populate the field. This isdemonstrated in FIG. 7 by Value 4 and Value 5 both being used topopulate Field 6. For example, a timestamp may need to be assembled froma time value and a date value. Similarly, an IP address may be assembledfrom two values, each containing an octet.

The normalized event conforming to the normalized schema 78 can havevarious fields. Some example fields are given by Table 2.

Furthermore, there are many ways to implement map 82. In one embodiment,the map 82 depends on the values of the received security event, whichin turn depends on the type of network device the agent 12 ismonitoring.

In one embodiment, all values are used to populate the fields of thenormalized schema 78. However, in other embodiments, certain values maynot be mapped, or mapped only after passing through a translator 80.After the map 82 is performed, the normalized event conforming to thenormalized schema 78 can be sent for further processing, such asaggregation, batching, transport, and correlation.

The time correction component 56 will now be described. The timecorrection component 56 can correct agent time and correct detect time.

Agent Aggregate Component

One embodiment of the agent aggregate component 58 is now described withreference to FIG. 8. As shown in FIG. 8, events 92 get stored in theevent buffer 88 of the agent aggregate component 58 through theoperation of a timer/counter gate 86. In one embodiment, the events 92have already been normalized by the agent normalize component 54 to aidthe aggregation process.

One of the fields of the normalized schema used by these normalizedevents 92 is a count field 94 that indicates how many times an event wasreceived. Prior to aggregation, this count field 94 can be initializedto indicate that the event has not yet gone through aggregation. In oneembodiment, the count field 94 is initialized to zero.

In one embodiment, the timer/counter gate 86 is implemented as a counterthat counts the number of events 92 entering the agent aggregatecomponent 58. For example, the counter can be configured to fill theevent buffer 88 with 30 events at a time. In another embodiment, thetimer/counter gate 86 is implemented as a timer that lets events throughfor a period of time. For example, the timer can be configured tocollect events 92 in the event buffer 88 for 5 minutes.

When the timer/counter gate 86 indicates that the event buffer 88 isready for aggregation, e.g. when the counter reaches a predeterminednumber or when the timer expires, the events 92 in the event buffer 88are passed to the aggregator 96. The function of the aggregator 96 is tocount the number of identical events in the event buffer 88 and tooutput each distinct event only once with the count field 94 indicatingthe number of times identical events were aggregated.

In FIG. 8, the events 92 labeled with the same letter symbolizeidentical events, and the events labeled with different letterssymbolize distinct events. Thus, in the example of FIG. 8, aggregator 96had recorded the events C,A,B,A,B,C,A,B and aggregated them to outputevent A,B,C to the output buffer 90. FIG. 8 also shows that theaggregator 96 has changed the count field 94 of these events 92 fromtheir initial values of zero, to the appropriate aggregated count forthe distinct events. Thus, e.g., event A has a count field of three.

The events 92 in the output buffer 90 can then be sent for furtherprocessing, such as batching and correlation. As illustrated in FIG. 8,the output buffer uses less than half of the memory that the inputbuffer uses. This conserves memory and reduces the bandwidth requiredfor sending the events 92 to the manager 14.

In one embodiment, the aggregator 96 determines which events areidentical based on a set of key fields.

In one embodiment, the field indicating the time of the event isexcluded from this set of fields compared, since identical events may bereported at different times. This type of aggregation does not preservethe precise time for all identical events, but does provides the highestdegree of efficiency. In one embodiment, the aggregator can note theearliest and the latest time for each identical event, and fill infields, e.g., an event_start and an event_end field, in events 92 tothat effect.

For one set of identical events, such as the events labeled A, after theaggregator 96 determines which events 92 belong in the set, theaggregator 96 outputs a single occurrence of the identical events. Forthat single occurrence, the aggregator 96 updates the count field 94 ofthe event to reflect the number of identical events in the set.

The output of the aggregator 96 is shown in FIG. 8 to be placed in anoutput buffer 90 until all events 92 in the event buffer 88 have beenaggregated. However, the aggregated events 92 being output from theaggregator 96 can be sent directly for further processing.

The security events can next be processed by the agent batch component60. The agent batch component 60 performs the batching of securityevents into event batches to be transmitted. Since there is a certainamount of overhead associated with transmitting events from an agent tothe agent manager 26, such as transport protocol overhead and systemcommunication overhead, it can improve overall performance of thenetwork security system to batch security events prior to sending themto the security manager, or other further processing.

The batching can be done according to a configurable time limit, e.g.transmitting a batch every twenty minutes, or according to a numberlimit, e.g. transmitting a batch when a hundred security events arereceived and collected. The batching can be simple or prioritized.

The agent resolver component 62 will now be described. The agentresolver component 62 is utilized to fill in incomplete addressdescriptions on event. Also, the agent resolver component 62 performsreverse DNS lookups to resolve hostnames and domains to INET address. Inaddition, the agent resolver component 62 performs DNS lookups toresolve hostnames and domains to INET address.

The agent 12 also includes an agent transport component 64. The agenttransport component 64 is where messages transmitted to the agentmanager 26 exit the agent 12 and messages transmitted from the agentmanager 26 enter the agent 12.

FIG. 9 is a flow chart illustrating a method 100, according to oneembodiment of the invention, of configuring an agent 12. The agent 12 ismodular in that the agent may be manually configured by user (e.g., atconsole/browser 16) with multiple different types of components.Furthermore, the agent 12 may be manually modified by a user (e.g., atconsole/browser 16) after it has been deployed. At block 102 theidentity of an agent 12 to be configured is identified. In the exemplaryembodiment, the agent is configured as a result of manual processing.

At block 108, a determination is made as to whether the agent 12requires time correction. Similar to the description above, the decisionis entered by a user and applied via console/browser 16.

At block 110, if the user does want to include a time correctioncomponent 56, manager 26 communicates via the network with agent 12, anduploads the necessary configuration information needed to update theconfiguration file associated with agent 12.

At block 112, a determination is made as to whether the agent 12requires aggregation within the agent 12.

At block 114, if the user does want to include aggregation, manager 26communicates via the network with agent 12 and uploads the necessaryconfiguration information needed to update the configuration fileassociated with agent 12.

At block 116, a determination is made as to whether the agent 12requires batching within the agent 12.

At block 118, if the user does want to include batching within the agent12, manager 26 communicates via the network with agent 12 and uploadsthe necessary configuration information needed to update theconfiguration file associated with agent 12.

At block 124, a determination is made as to whether any other componentswithin the agent 12 need to be reconfigured. At block 126, theadditional components 66 are identified. At block 128, manager 26communicates via the network with agent 12 and uploads the necessaryconfiguration information needed to update the configuration fileassociated with agent 12.

At block 130 the agent 12 configures itself according to theconfiguration file and begins running with the updated configuration.

While method 100 provided for a user stepping through a process in whicha decision is made about each of a multiple of components, the user isnot required to follow such a process. For example, a user may simplymodify the time correction component 56 of an agent 12 via theconsole/browser interface 16. In response, the configuration fileassociated with the agent is updated at manager 14 and the agent 12configuration information is sent by agent manager 26 to agent 12. Agent12 updates its configuration according to the configuration informationit receives from agent manger 26. Thus, through entries made atconsole/browser interface 16 users may create or modify agents 12without making source code changes. Such entries for example may includesimply selecting components (e.g., agent aggregate component 58) fromdrop down lists. In one embodiment the agent is restarted in order forthe changes to take effect.

FIG. 10 is a flow chart illustrating a method 136, according to oneembodiment of the invention, of automatically altering the operation ofan agent 12.

At block 138, manager 14 determines that as a result of securityinformation received the agent needs to initiate a set of instructions(e.g., UNIX shell script) in response.

At block 140, agent manager 26 communicates the set of instructions viaa network to agent 12.

At block 142, the set of instructions are received by agent 12 andinitiated according to the direction of the agent manager 26.

Bi-Directional Communication

FIG. 11 is a diagrammatic representation of bi-directional communicationbetween an agent 12 within a host and an agent manager 26. In additionto the components described in FIGS. 4 and 5 earlier, a heartbeat sendpath 146 is shown. The heartbeat send path 146 provides a section of theroute that heartbeat messages will take during transmission from anagent 12 to an agent manager 26. Also, a heartbeat response message path150 is shown as the route that the heartbeat response message from theagent manager 26 to the agent 12 will take. Included within theheartbeat response message path 150 is a heartbeat receiver 148. Aheartbeat message is a type of message sent from an agent 12 to an agentmanager 26 to determine if changes need to be made to the agent 12 or ifthe agent 12 needs to take other actions (e.g., launch a UNIX shellscript).

FIG. 12 is a flow chart illustrating a method 154, according to oneembodiment of the invention, showing bi-directional communicationbetween an agent 12 and an agent manager 26.

At block 156, a heartbeat message is sent from an agent 12 to the agentmanager 26. The interval of time between which heartbeat messages aresent is configurable and may be set in the agent 12 configuration file(e.g., one heartbeat message every ten seconds). In the exemplaryembodiment, the heartbeat message is sent from the agent normalizecomponent 54 via the heartbeat send path 146 to the agent transportcomponent 64. The agent transport component 64 then forwards theheartbeat message (e.g., via the HTTP protocol) to the agent manager 26.

At block 158, the agent manager 26 receives the heartbeat message. Atblock 160, the agent manager 26 determines which agent 12 sent theheartbeat message. In the exemplary embodiment, the agent manager 26makes this determination by comparing a unique identifier includedwithin the heartbeat message against a table of identifiers. The tableof identifiers includes a unique identifier for each agent 12 associatedwith the agent manager 26.

At block 162, the agent manager 26 determines what (e.g., commands,instructions, etc.) to include in a response message to the agent 12.The agent manager 26 makes the determination based on user initiatedinstructions (e.g., configuration updates), and rules included withinthe rules engine 18. An example of user initiated instructions may beinstructions requesting that the agent aggregate component 58 be removedfrom the agent. In the exemplary embodiment, the user would enterinstructions via the console/browser interface 16. The instructions arethen forwarded to the agent manager 26, where they will be includedwithin a response message to the agent. While the example describes userinitiated instructions to reconfigure the agent 12, user initiatedinstructions include any instructions to alter the configuration oralter the actions of the agent 12.

The rules engine relies on a variety of factors, including previousevent data received from the agent 12, the current security level, anduser settings. An example of how the rules engine 18 affects what isincluded in a response message may be the automatic generation of a setof instructions (e.g., UNIX shell script, LINUX shell script, Windowsbatch file, etc.) in response to criteria meeting conditions in therules engine 18. Such a set of instructions in one example might tell afirewall to shut down a communications port.

At block 164, the agent manager 26 prepares the response message to besent to the agent 12. The response message includes commands to launchthe instructions determined at block 162. In the exemplary embodiment,the commands include pause, stop, restart, reconfigure, and a command tolaunch the automatically generated instructions discussed above. Thepause command prevents the transmission of events to the agent manager26. However, the pause command does not prevent the processing ofevents. The stop command prevents the receipt of events at the agentmanager 26 from the agent 12. But the heartbeat messages from the agent12 to the agent manager 26 will continue after a stop command has beeninitiated. The restart command allows previously stopped events to bereceived, processed, and transmitted from the agent 12 to the agentmanager 26 once again. The reconfiguration command alters theconfiguration of an agent 12, and includes the user initiatedinstructions entered at block 162. The reconfiguration command providesfor adding, deleting, or modifying instructions within an agent 12configuration file.

At block 166, the agent manager 26 sends (e.g., via the HTTP protocol)the response message to the agent transport component 64. In theexemplary embodiment, the response message is sent back via the sameport through which the heartbeat message was received. The same path isused to send heartbeat messages and response messages resulting inbi-directional communication between agents 12 and the agent manager 26.At block 167, the agent transport component 64 passes the responsemessage to a heartbeat receiver 148 associated with the agent 12.

At block 168, the heartbeat receiver 148 deserializes the responsemessage and forwards it to the agent normalize component 54. Throughdeserialization, the message is converted into an object which isintelligible by the agent normalize component 54. At block 170, theagent normalize component 54 interprets the response message todetermine if any commands or configuration control information wasincluded in the response message.

At block 172, the agent normalize component 54 takes any necessaryaction (e.g., pause, stop, restart, reconfigure, configuration controls,etc.) corresponding to the response message. For example, the responsemessage may include a configuration command and the necessaryconfiguration information. The configuration may for example requestthat the instruction to include the agent aggregate component 58 in theagent 12 configuration file is to be deleted.

Thus, a network security monitoring system employing bi-directionalcommunication between a server-based software agent manager and modularsoftware agents has been described. In the foregoing description, thevarious examples and embodiments were meant to be illustrative of thepresent invention and not restrictive in terms of their scope.Accordingly, the invention should be measured only in terms of theclaims, which follow.

1. A method performed by a processor-based manager of providingbi-directional communication, comprising: receiving a heartbeat messagefrom a software agent, the software agent configured to periodicallysend the heartbeat message and further configured to report a securityevent, wherein the security event originated in an event log that wasgenerated by a network component, and wherein the security eventcomprises information about operation of the network component; and inresponse to receiving the heartbeat message: identifying the softwareagent; determining how to respond to the heartbeat message, includingdetermining a rule-initiated instruction to send to the software agent;preparing a response message that includes the rule-initiatedinstruction; and sending the response message to the software agent. 2.The method of claim 1 wherein the heartbeat message is sent from thesoftware agent at set intervals.
 3. The method of claim 2 wherein theset intervals are configurable.
 4. The method of claim 1 whereinidentifying the software agent comprises: parsing the heartbeat messagefor identity information; and comparing the identity information againsta table of known software agents.
 5. The method of claim 1 whereindetermining how to respond to the heartbeat message further includesdetermining a user-initiated instruction to send to the software agent,and wherein the response message further includes the user-initiatedinstruction.
 6. The method of claim 5 wherein user the user-initiatedinstruction comprises a command to modify the software agent'sconfiguration.
 7. The method of claim 5 wherein the user-initiatedinstruction comprises a command to stop or pause the software agent. 8.The method of claim 1 wherein rules the rule-initiated instructioncomprises a UNIX shell script.
 9. The method of claim 1 wherein theheartbeat message and the response message are transmitted on abi-directional communication link between the software agent and anagent manager.
 10. The method of claim 1 further comprisingdeserializing, at the software agent, the response message.
 11. Asystem, comprising: a bi-directional communication link between asoftware agent included within a host machine and a server-based agentmanager, wherein the software agent is configured to periodically send aheartbeat message and further configured to report a security event,wherein the security event originated in an event log that was generatedby a network component, and wherein the security event comprisesinformation about operation of the network component; a first processorcomprising: an agent interface component configured to transmit a firstmessage onto and receive a second message from the bi-directionalcommunication link; and an agent heartbeat receiver component configuredto deserialize the second message received by the agent interfacecomponent; and a second processor comprising an agent-manager interfacecomponent configured to receive the first message from thebi-directional communication link and to transmit the second messageonto the bi-directional communication link, wherein the second messageincludes a rule-initiated instruction to send to the software agent. 12.The system of claim 11 wherein the first message comprises a heartbeatmessage.
 13. The system of claim 11 wherein the agent interfacecomponent is further configured to transmit the first message at setintervals.
 14. The system of claim 13 wherein the set intervals areconfigurable.
 15. The system of claim 11 wherein the first message isreceived at the agent manager.
 16. The system of claim 11 furthercomprising an agent-manager identification component to identify theagent by parsing the first message for identity information andcomparing the identity information against a table of known softwareagents.
 17. The system of claim 11 wherein the agent-manager interfacecomponent transmits the second message in response to receipt of thefirst message.
 18. The system of claim 11 wherein the second messageincludes an instruction related to the configuration and control of thesoftware agent.
 19. The system of claim 11 wherein the second messagefurther includes a user-initiated instruction to send to the softwareagent.
 20. The system of claim 11 wherein the rule-initiated instructionis automatically generated.
 21. A computer storage medium, having storedthereon computer-readable instructions, which when executed in acomputer system, cause the computer system to: receive a heartbeatmessage from a software agent, the software agent configured toperiodically send the heartbeat message and further configured to reporta security event, wherein the security event originated in an event logthat was generated by a network component, and wherein the securityevent comprises information about operation of the network component;and in response to receiving the heartbeat message: identify thesoftware agent; determine how to respond to the heartbeat message,including determining a rule-initiated instruction to send to thesoftware agent; prepare a response message that includes therule-initiated instruction; and send the response message to thesoftware agent.
 22. The computer storage medium of claim 21 whereinidentifying the software agent comprises: parsing the heartbeat messagefor identity information; and comparing the identity information againsta table of known software agents.
 23. The computer storage medium ofclaim 21 wherein determining how to respond to the heartbeat messagefurther includes determining a user-initiated instruction to send to thesoftware agent, and wherein the response message further includes theuser-initiated instruction.
 24. The computer storage medium of claim 23wherein the user-initiated instruction comprises a command to modify thesoftware agent's configuration.
 25. The computer storage medium of claim23 wherein the user-initiated instruction comprises a command to stop orpause the software agent.
 26. The computer storage medium of claim 21wherein the rule-initiated instruction comprises a UNIX shell script.